It is frequently necessary to mount or hold objects in place at or near the edge of a table or other structure having a protruding edge. An example of this includes the need to secure an umbrella shaft to the edge of a table or bannister so that the umbrella provides shade for persons at or near the structure. Another example includes the need to firmly hold an article, such as a piece of wood, to the edge of a table so that the article may be worked on or with.
C-clamp type clamping brackets are a type of bracket that is well known and traditionally used in such situations to provide the retention function. A C-clamp bracket is a bracket having a shape like the letter C, with an extensible urging member for changing the width of the slot of the C. C-clamps are useful because they provide firm gripping forces and are easy to take on and off. One drawback to C-clamp type brackets, however, is that they provide only a single point gripping force. That is, the clamping force of the C-clamp is provided at a single point. Large objects, or objects having a curved surface, such as an umbrella pole, are therefore difficult to hold with a C-clamp. In such situations, a plurality of distributed C-clamps must be employed to provide an adequate clamping function. Having to apply multiple clamps, however, defeats the convenience, purpose and utility of the clamp itself.
Efforts to improve such systems have led to continuing developments to improve their versatility, practicality and efficiency.